Zoetis’ Portela® (relfovetmab) Gains Positive CVMP Opinion for First Long-Acting Anti-NGF Therapy to Relieve Osteoarthritis Pain in Cats
Zoetis Inc., a global leader in animal health, announced a major regulatory milestone as the Committee for Veterinary Medicinal Products (CVMP) of the European Medicines Agency (EMA) adopted a positive opinion recommending marketing authorization for Portela® (relfovetmab). Portela is an innovative monoclonal antibody (mAb) therapy designed to alleviate pain associated with osteoarthritis (OA) in cats, a condition that is far more prevalent than many pet owners and even veterinarians realize.
If granted final approval by the European Commission later this year, Portela will become the first long-acting anti-nerve growth factor (NGF) monoclonal antibody therapy for cats. The product is uniquely formulated to provide up to three months of pain relief with a single injection, marking a significant step forward in feline medicine and chronic pain management.
A Breakthrough in Feline Osteoarthritis Treatment
Osteoarthritis, or OA, is one of the most common chronic diseases in cats, characterized by inflammation and progressive degeneration of the joints. It causes persistent pain, stiffness, and impaired mobility, significantly affecting quality of life. While OA is incurable, effective management of pain and mobility issues is essential to improving outcomes for affected animals.
Zoetis’ Portela specifically targets nerve growth factor (NGF), a key mediator in the transmission of pain signals associated with osteoarthritis. By blocking NGF, Portela disrupts the pain pathway, thereby helping to relieve discomfort and improve mobility. Unlike traditional pain medications, which require frequent dosing and can be difficult for cat owners to administer consistently, Portela is administered by veterinarians as an injection just four times a year.
The positive CVMP opinion was based on comprehensive safety and efficacy data submitted by Zoetis. Clinical trials demonstrated that Portela was not only effective in alleviating OA-related pain but also well tolerated by cats, including those with pre-existing kidney disease at IRIS stages 1, 2, or 3. This is an important consideration, as older cats often suffer from multiple health conditions that can complicate treatment options.
Meeting an Unmet Need in Veterinary Care
Despite OA being widespread among cats, the condition is often underdiagnosed and undertreated. Studies suggest that up to 40% of cats show clinical signs of osteoarthritis, yet only about 18% are formally diagnosed by veterinarians. One reason for this gap is that symptoms of OA in cats can be subtle—reduced jumping, less grooming, or changes in behavior are often misattributed to “normal aging” rather than underlying pain.
This underdiagnosis means that millions of cats endure chronic pain without receiving appropriate treatment. Chronic pain, beyond impairing movement, has been shown to negatively impact sleep quality, social interactions, and even cognitive function in cats. By offering a convenient, long-acting treatment, Portela could empower veterinarians to intervene earlier and more effectively, improving the lives of both cats and their owners.
Dr. Rob Polzer, Executive Vice President and President of Research and Development at Zoetis, emphasized the significance of this step:
The CVMP’s positive opinion for Portela represents a significant step forward in advancing feline pain management. The long-acting antibody properties of Portela and its unique binding site to NGF will soon offer veterinarians and cat owners in the European Union a new option to alleviate pain associated with osteoarthritis, thereby helping to improve the quality of life for affected cats.
Building on Zoetis’ Legacy in Monoclonal Antibody Innovation
Portela is not Zoetis’ first anti-NGF monoclonal antibody therapy. The company previously launched Solensia® (frunevetmab), the world’s first monoclonal antibody approved to control OA pain in cats. Unlike Portela, which is designed to last three months per injection, Solensia provides one month of relief and has already been approved in more than 40 countries.
Real-world data from over four years of use has validated the effectiveness of Solensia in relieving pain and enhancing quality of life for cats with OA. However, for many cat owners, the monthly vet visits required for administration can be challenging. Portela addresses this concern directly by offering a three-month dosing interval, reducing the logistical burden for pet owners while maintaining continuous pain relief for their cats.
Richard Goldstein, DVM, DACVIM, DECVIM-CA, Global Chief Medical Officer and Head of Medical Affairs at Zoetis, highlighted the company’s commitment to advancing veterinary medicine:
If approved, Portela will be a new, science-driven solution designed to support long-term comfort and mobility for cats—with the added benefit that pet owners only need to bring their cats in for an injection once every three months. This is a testament to the value we place at Zoetis on meaningful innovation in feline medicine, solving for the unmet needs of our feline patients and their families. Four years ago in the EU, we introduced the first monoclonal antibody therapy to control pain associated with OA in cats, and we look forward to providing veterinarians with another innovative tool to help them improve the quality of life for the animals in their care.
The Broader Challenge of Osteoarthritis in Cats
OA in cats presents unique challenges compared to dogs or humans. Cats instinctively mask pain and discomfort, a survival trait carried over from their evolutionary history. As a result, clinical signs are easily overlooked until the disease has significantly progressed.
Moreover, many cats are difficult to medicate at home. Oral medications can be stressful for both pet and owner, and compliance often suffers. Injectable therapies like Portela not only provide more consistent pain management but also reduce the emotional and physical stress associated with daily or weekly treatments.
The launch of Portela could also raise awareness of OA among veterinarians and pet owners, helping to close the diagnosis gap. By having a convenient, long-lasting treatment available, veterinarians may be more proactive in screening for and diagnosing OA in routine checkups, ultimately leading to better care outcomes.
Safety Profile and Considerations
Like all medicines, monoclonal antibody therapies can carry risks of side effects. For Solensia, the most common side effects reported were hair loss, itching, and dermatitis, which may affect up to 1 in 10 cats. Rare side effects include injection site reactions and skin lesions (1 in 1,000 cats), while very rare adverse events such as anaphylaxis occur in fewer than 1 in 10,000 cats.
While Portela is still under regulatory review, its clinical trial data suggest it is generally well tolerated, including by cats with kidney disease—an important safety consideration given the high prevalence of renal conditions in older cats.
Next Steps Toward Approval and Commercial Launch
Following the CVMP’s recommendation, the European Commission is expected to issue a final decision on Portela’s marketing authorization during the fourth quarter of 2025. If approved, Zoetis plans to commercially launch the therapy in the European Union in 2026.
The approval of Portela would further strengthen Zoetis’ leadership in the animal health sector, particularly in the fast-growing field of monoclonal antibody therapies for companion animals. It would also reinforce the company’s position as an innovator committed to addressing unmet medical needs in veterinary medicine.
